Nnamdi Asomugha, presumably the first cornerback off the bench, was limited in practice today with a collarbone injury. Asomugha, 32, has been wearing a non-contact jersey in practice since the third preseason game against the Vikings on Aug. 25, when he was presumably hurt. Along with 10 defensive starters, Asomugha did not play in the preseason finale in San Diego last week.

One thing remains clear about the season opener, however: The 49ers’ third cornerback will play plenty with Green Bay often employing three-wide-receiver formations.

Last year, No. 3 cornerback Chris Culliver played 86 percent of the defensive snaps (114 of 132) in two games against the Packers, according to Pro Football Focus. Culliver played 61 percent of the snaps (706 of 1,149) in San Francisco’s other 17 games.

Culliver routinely matched up with Green Bay wide receiver Jordy Nelson, who was not listed on today’s injury report after undergoing knee surgery in early August. Nelson had 10 catches for 110 yards in the two games against the 49ers last year. In the 49ers’ season-opening 30-22 win at Lambeau Field, Culliver batted away a deep fourth-down pass intended for Nelson to secure the win.

Inside linebacker Patrick Willis was not listed on the injury report after he practiced with only a glove on his broken right hand. During a pass-catching drill, Willis caught passes, but assistant coach Peter Hansen took a little steam off his fastball when it was Willis’ turn.

Willis said his doctor has estimated his bone will be completely healed in about three-and-a-half weeks. He hopes to play without added protection on his hand, but he’s been looking at different devices in the event it’s necessary.